I am definitly getting that book you guys were talking about. I'm 21 now. I figure by the time I'm like 30, I'll have this down to an art, if I like it. I've been thinking about doing this for a while. And so I thought, if I can handle calculus, physics, and chem., I should be able to port some stinkin' heads. I've just been way too afraid of messing up, but I guess you have to mess up to learn sometimes.

Anyhow, OT, but a guy in Fayetteville told me that he benched his LT1 castings at 320cfm
I am very skeptical. I thought the most you could get was 290cfm is you were lucky. Anyone believe this guy?

 

I believe one time Phil posted some pics of him getting approx. 305 cfm's out of a set of stock LT1 castings, but Ai knows what they are doing.

 

I know you can measure cfm, but can you measure velocity at certain points?

Do you believe that that one company down here in fayetteville could do 320cfm? That would defeat my need for the time being to get 18* heads.

I'm thinking now I will just get the lt1 heads ported up, mill and port the intake, and bump the compression up to 12.

 

WOW! Not another head porting thread!

I am going to go out on a limb here. Lets break some rules!

1. If you are planning on working on a set of ltx heads, burn vizards book (sorry dave). The port biasing theories work great on slow heads. You have actually got a head to work with though. If your buddy has a set of 461's laying around...then this is your book. Otherwise, it's the school of hard knocks.

2. 95% of the power is found in the SSR , venturi, and chamber. I remember hearing the comment of thousands not meaning anything...In the real world, .010 is equal to about 20 football fields.

3. Anybody can buy a grinder, very few can use one. Work on grinder control before considering porting.

4. For a "race" prep'd ltx casting, their is no safe zone. Most of the street stuff you see hurts power more then helps. A few simple modifications, and you should have a fairly strong head.

5. Buy a set of inside mics and a 6" caliper. you need them.

a little instruction. (don't worry about flow, just follow these to the T and you should be happy).
1. the throat (or venturi) is the portion of the seat that is perpindicular to the deck. Make this 88% of the valve size, no bigger, no smaller. Intake seat should be 45 @ .060, top cut 28 @ .60 blended to chamber, bottom cut 58 @ .080. blend bottom into bowl.

2. Widen the SSR .075 more towards the fast wall (the one that is straight). MAKE SURE YOU KEEP THE SAME RADIUS ON BOTH SIDES AS FACTORY! blend the bottom of the seat into the bowl with a cartridge roll.

3. Make the roof of the ports flat, go up .025. keep elevation and shape as is on radius next to fast wall.

4. make fast wall (the straight one) as straight as possible without going into the head bolt hole. Leave .030 of material for support.

Clean everything else up with a 60 grit roll.

 

Also, Someone may be concerned that I am giving away secrets...If you port heads for a living and don't know these simple tips, or are willing to share them, than maybe you should go back to making pizza's.

These practices that are outlined above are very simple to understand. Doing it is another thing. Wait till you try blending the top cut into the chamber. Some guys today still can't do this correctly after 20 years of experience. take your time and practice, practice, practice...and then practice some more....


did I say anything about practice?

have fun...AND WEAR A DUST MASK / EAR PROTECTION!


And YES to answer the ellusive questions everybody asks...there ARE ltx heads that go over 300cfm... We have had a program for this since 98...how well do they work on a street car?...not very.

 

Why don't they work very well on a street car?

If Lloyd Elliot's 270cfm packages are taking people around 450rwhp, should 320cfm take you to close to 500rwhp? I just can't get over it. That is so great for an ltx head. Would the lt4 head have more potentional for flow? I am thinking about getting lt4's because if the lt1 can flow 320, then the lt4 should be able to flow 340. Those numbers are close to that of a 18* head.

What would be better for streetablity? An 18* head flowing 320 or an ltx head flowing 320?

Keep in mind, my idea of streetability is about 10mpg city and 20mpg highway.

 

Kurt....

As I said before 450rwhp don't just happen.

more flow doesn't always = more hp

I have a feeling that the heads that airflowdevelopment is talking about are for drag racing so little differences like seat widths, how thin the casting is in some areas and the RPM range that the heads are usefull in keep them from being a street car head.... oh and probably some welding and in the end cost.

Head porting is more of a art with hard science behind it. Hell I majored in sculpture and I haven't decided to take the plunge and do it yet and I've been playing with motors for a long time....

Bret

 

Welding would be an understatement...

If I get a chance, I have a set in development right now. I will snap some pics for you guys.

Kurt,
These heads go on cars that leave vertical, turn 9200+ revs and consume 3/4 of a gallon in 1320 feet....If you must have a set, their are no returns and the cost is north of $7k. Your best bet is a set of 18 degree GM heads or the knockoffs which are even cheaper, rolled out. 700HP NA out of a 370" ltx...no problem. And you could take it to the ice cream shop once and a while.

Dennis

 

What costs $7000? Porting the heads?

 

Yes,because it IS rocket science!!!!!

 

For those that enjoy discussing flow#'s and specifically on LT1 castings this may be an interesting read. Yes, we can get over 300cfm with no welding or other tricks. Scroll down to post#26.

http://web.camaross.com/forums/showthread.php?t=295229

 

Kurt,
Our current "C" heads require about 210 hours of prep work. At that amount of time $7400.00 is a bargain. These heads propel 3410lbs to 8.96 seconds in 1320 feet.

Like I said, these are not for the street. Much easier ways to go faster for less. The point of this thread was to provide some simple concepts to make the ltx heads work for the DIY guy. Not to upset Aisr.

Thanks
Dennis

 

I know this has already been stated.... But actual numbers are not so much what I need to look at. Just dyno numbers and track numbers, right?

Were you saying that a 320cfm head has taken someone to 8.xx seconds NA?

 

No offense taken....we agree most would not be willing to pay for the work that goes into these ports.

 

I very much appreciate that a couple of experts have decided to post on this topic. Thanks!

In the above post, note the phrase "much easier ways to go faster for less". A set of $7,000 heads makes "sense" only in the context of the need to make huge hp from a limited displacement without a power adder. IOW, certain types of racing. Or, if you are rich or just eccentric and want bragging rights. Don't forget that to go fast with those $7K heads you need at least another $15K in supporting parts. You are going to have to turn big rpm, meaning a strong but light (= expensive) rotating assy, an expensive induction and exhaust system, valvetrain, and so on.

Where I am coming from is that 6-800hp won't cut it these days if you want to be a big dog. 900-1000+ is where you need to be. So, before you start you need to decide where you want to end up and take a route that will get you there.

Rich